Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$118.32	7.365%	$127.0343	$127.03	$127.05	$127.00
Purchase #2	$152.42	8.804%	$165.8391	$165.84	$165.85	$165.80
Purchase #3	$62.30	12.759%	$70.2489	$70.25	$70.25	$70.20
Purchase #4	$92.74	11.474%	$103.381	$103.38	$103.40	$103.40
Purchase #5	$175.81	12.261%	$197.3661	$197.37	$197.35	$197.40
Purchase #6	$155.80	12.354%	$175.0475	$175.05	$175.05	$175.00
Purchase #7	$80.55	11.384%	$89.7198	$89.72	$89.70	$89.70
7 purchase totals =	$837.94		$928.6367	$928.64	$928.65	$928.50